The Journal of Organic Chemistry
Article
(17) For diastereoselective cyclopropanations directed by −NHCOR
(31) IR bands corresponding to the AcOEt solvent were subtracted
following a background replacement and the spectra were baseline
corrected at 1660 cm−1.
́
moieties, see: (a) Csatayova, K.; Davies, S. G.; Lee, J. A.; Ling, K. B.;
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́
(32) Iodine was described by Glukhovtsev’s modification of the 6-
311G basis set: (a) Glukhovtsev, M. N.; Pross, A.; McGrath, M. P.;
Radom, L. J. Chem. Phys. 1995, 103, 1878−1885. (b) Glukhovtsev, M.
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3407. This basis set has been previously applied to the study of
cyclopropanations mediated by zinc carbenoids: (c) Eger, W. A.;
Zercher, C. K.; Williams, C. M. J. Org. Chem. 2010, 75, 7322−7331.
(33) We hasten to note that, in the absence of experimental data on
the aggregation of 7a, the choice of implicit solvation and monomeric
species provides results that must be interpreted as general trends
rather than definite values. For a general review on the impact of
aggregation upon reactivity, see: McNeil, A. J.; Ramirez, A.; Collum, D.
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(34) Solvated analogues of structure 10 (n ≠ 0) and complexes 11−
16 could not be located presumably owing to steric hindrance.
(35) Bissette, A. J.; Fletcher, S. P. Angew. Chem., Int. Ed. 2013, 52, 2−
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(36) Likewise, the addition of 20% v/v of an ended reaction to the
reaction between 7a and Zn(CH2I)2 mediated the loss of the
sigmoidal profile and accelerated the cyclopropanation. See Supporting
Information for details.
(37) Espenson, J. H. In Chemical Kinetics and Reaction Mechanisms;
McGraw-Hill: New York, 1995; pp 7−81.
(38) A first-order dependence on the concentration of zinc carbenoid
has been reported previously: Blanchard, E. P.; Simmons, H. E. J. Am.
Chem. Soc. 1964, 86, 1347−1356.
(39) Nakamura, M.; Hirai, A.; Nakamura, E. J. Am. Chem. Soc. 2003,
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(40) Boersma, J. In Comprehensive Organometallic Chemistry;
Wilkinson, G., Ed.; Pergamon Press: New York, 1984: Vol. 2, Chapter
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(41) From Sigma-Aldrich: ≥99.99% ZnI2, 25 g, $143.50 (230014).
(42) (a) Cheng, D.; Huang, D.; Shi, Y. Org. Biomol. Chem. 2013, 11,
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(43) Anderson, N. G. In Practical Process Research and Development;
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(44) (a) For a recent discussion of the effect of zinc oxo-complexes
derived from water on related reactions, see: Fandrick, D. R.; Reeves, J.
T.; Bakonyi, J. M.; Nyalapatla, P. R.; Tan, Z.; Niemeier, O.; Akalay, D.;
Fandrick, K. R.; Wohlleben, W.; Ollenberger, S.; Song, J. J.; Sun, X.;
Qu, B.; Haddad, N.; Sanyal, S.; Shen, S.; Ma, S.; Byrne, D.; Chitroda,
A.; Fuchs, V.; Narayanan, B. A.; Grinberg, N.; Lee, H.; Yee, N.;
Brenner, M.; Senanayake, C. H. J. Org. Chem. 2013, 78, 3592−3615
and references cited therein..
Roberts, P. M.; Russell, A. J.; Thomson, J. E. Tetrahedron 2010, 66,
8420−8440. (c) Davies, S. G.; Ling, K. B.; Roberts, P. M.; Russell, A.
J.; Thomson, J. E. Chem. Commun. 2007, 4029−4031. For reviews on
directed cyclopropanations, see: (d) Charette, A. B.; Marcoux, J.-F.
Synlett 1995, 1197−1207. (e) Hoveyda, A. H.; Evans, D. A.; Fu, G. C.
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(18) We represent Furukawa’s reagent as EtZnCH2I for simplicity.
Spectroscopic studies, however, have revealed that EtZnCH2I is in
equilibrium with Et2Zn and Zn(CH2I)2: (a) Charette, A. G.; Marcoux,
J.-F. J. Am. Chem. Soc. 1996, 118, 4539−4549. (b) Denmark, S. E.;
O’Connor, S. P. J. Org. Chem. 1997, 62, 3390−3401.
(19) For a recent review on the dynamic behavior of organozinc
compounds, see : Guijarro, A. In The Chemistry of Organozinc
Compounds; Rappoport, Z., Marek, I., Eds.; Wiley: Chichester, 2007;
Chapter 6.
(20) The ethane resonance at 7.0 ppm could be detected by 13C
NMR spectroscopy at −10 °C.
(21) (a) Noltes, J. G.; Boersma, J. J. Organomet. Chem. 1969, 345−
355. (b) Coates, G. E.; Ridley, D. J. Chem. Soc. 1966, 1065−1069.
(22) (a) Schmidt, S.; Schaper, R.; Schulz, S.; Blaser, D.; Wolper, C.
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(23) Charette, A. B.; Marcoux, J.-F. J. Am. Chem. Soc. 1998, 120,
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(24) For IR spectra assignments of CH2I2 and CD2I2, see: Ford, T. A.
J. Mol. Spectrosc. 1975, 58, 185−193.
(25) The problematical insertion of CH2I2 into related ROZnEt
species compared with ZnEt2 has been noted previously: Charette, A.
B.; Brochu, C. J. Am. Chem. Soc. 1995, 117, 11367−11368.
(26) Such exchange would afford mixtures of iodomethylzinc amidate
8b, Zn(CH2I)2 and EtZnCH2I that, by analogy with the rapid
reactivity of Et2Zn with the first and second equivalent of CH2I2, could
consume the excess CH2I2 allowing for formation of 8b and
Zn(CH2I)2. For a review, see: Blake, A. J.; Shannon, J.; Stephens, J.
C.; Woodward, S. Chem.Eur. J. 2007, 13, 2462−2472.
(27) 13C NMR spectra of samples containing Et2Zn (0.15 M) and 2
equiv 13CH2I2 prepared at 0 °C in AcOEt also showed the same
resonance at −17.3 ppm. For 13C NMR spectroscopic studies on
Zn(CH2I)2, see refs 15 and 18.
(28) (a) Charette, A. B.; Molinaro, C.; Brochu, C. J. Am. Chem. Soc.
2001, 123, 12160−12167. (b) Charette, A. B.; Marcoux, J.-F.;
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(45) Richards, P. I.; Boomishankar, R.; Steiner, A. J. Organomet.
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(29) Zinc amide aggregates: (a) Schmidt, S.; Schaper, R.; Schulz, S.;
̈
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(47) For general discussions on the effect of Lewis acids on
cyclopropanations, see: (a) Cornwall, R. G.; Wong, O. A.; Du, H.;
Ramirez, T. A.; Shi, Y. Org. Biomol. Chem. 2012, 10, 5498−5513.
(b) Charette, A. B. In The Chemistry of Organozinc Compounds;
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(30) Zinc complexes and reactions are routinely influenced by the
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